1. Field of the Invention
This invention relates to the cutting of vegetation, and more particularly, it relates to the cutting of vegetation using a flexible, non-metallic cutting line extending from a rotating head into a cutting plane.
2. Description of Prior Art
Various types of devices have been proposed for many years to facilitate the removal of vegetation by mowing, trimming, edging and like cutting operations. In general, these devices have employed a metal blade to effect vegetation removal. Devices of this nature employ prime movers such as electric and gasoline motors. As a result, rotating metal blades can inflict serious and terrible injury upon the user.
In about 1960, there was developed in Europe a trimmer/edger unit employing a flexible polymeric line extending from a rotating head for cutting vegetation. This unit did not work properly because of several defects in structure and operating parameters. In the United States of America, practical vegetation cutting devices using flexible, non-metallic lines carried upon a rotating head were developed. The devices are shown in U.S. Pat. Nos. 3,708,967, 3,826,068 3,859,776, 4,035,912, 4,052,789 and 4,054,992. These patented devices have met outstanding success in that these American developments are probably the safest electrical or gasoline-powered tools yet invented for vegetation cutting, edging and trimming operations.
The devices shown in these patents employ a flexible cutting line, such as manufactured from Nylon.RTM. polymer. The cutting line is carried usually upon a spool internally of a rotating head. When desired to replenish the line or to extend an additional length of it, the rotation of the head was stopped and line manually extended from the spool. This line extension procedure in the patented devices has been found to be convenient, simple and reliable. In many of the more powerful devices, especially those powered by d.c. electric motors, a system to extend the cutting line from the head without interrupting cutting operations was desired. The present invention is a device for cutting vegetation in the nature of the patented devices, wherein a durable and reliable, positive clutch-like mechanism is employed for extending selectively, the cutting line in a certain length from the head. More particularly, this novel apparatus is easy to operate, rugged in construction and has no complicated mechanisms. A ball member on the head is depressed while the head is rotating. The line is pulled by centrifugal force from an internal spool released for rotation a certain angular displacement in the head. The spool is under positive control before, during and after the cutting line is extended. At no time can the spool "free wheel" in the head. Other unique features of the present invention will be apparent from the following description.